Characteristics of Different Molecular Weight Chitosan Films Affected by the Type of Organic Solvents

ABSTRACT: Chitosan films were prepared using 3 chitosan molecular weights and 4 organic acid solvents without plasticizer. Tensile strength (TS) and elongation (E) ranged from 6.7 to 150.2 MPa, and from 4.1 to 117.8%, respectively. Water vapor permeability (WVP) and oxygen permeability (OP) ranged from 0.3 to 0.7 ng-m/m²-s-Pa and OP from 0.4 to 5.8 × 10 ⁻⁸ cc/m²-day-atm, respectively. TS increased with chitosan molecular weight. Acetic acid resulted in the toughest films followed by malic, lactic, and citric acid, respectively. Films prepared with citric acid had the highest E values. WVP was not influenced significantly by the molecular weight of chitosan. OP of films prepared with malic acid was the lowest, followed by acetic, lactic, and citric acid.     

Physical properties of PVOH/chitosan-blended films cast from different solvents

Homopolymer films of chitosan and polyvinyl alcohol (PVOH) and blended films consisting of PVOH and chitosan were cast from different organic acid solvents: acetic acid (AA), citric acid (CA), lactic acid (LA) and malic acid (MA) and characterized for mechanical and barrier properties. Intermolecular interactions were investigated with FTIR. Cross-linking and interactions with the solvent system resulted in a wide range of properties. Also, the effect of blends and acid solvent on the mechanical properties [tensile strength (TS), % breaking elongation (%BE)] and barrier properties [water vapor permeability (WVP)] was investigated. The organic acid used as a solvent affected mechanical properties and the WVP of PVOH/chitosan films blends. TS and %BE of PVOH/chitosan films were 13.5–221.9 Mpa and 5.2–451.8%, respectively. The WVP ranged from 0.19 to 0.62 ng m/m² s Pa. The range of properties, both intermediate from the component polymers and extending beyond either individual component suggests molecular interactions and cross-linking within the blends. Elucidation of these interactions continues.     

Effect of Molecular Weight,Acid, and Plasticizer on the Physicochemical and Antibacterial Properties of β‐Chitosan Based Films

Abstract: Effects of chitosan molecular weight (1815 and 366 kDa), type of acid (1% acetic, formic, and propionic acid, or 0.5% lactic acid) and plasticizer (0, 25% glycerol or sorbital w/w chitosan) on the mechanical, water barrier, and antibacterial properties of β‐chitosan films were investigated. Tensile strength (TS) of high molecular weight (Hw) films was 53% higher than that of low molecular weight (Lw) ones, acetate, and propionate films had the highest TS (43 and 40 MPa) among tested acids, and plasticizer‐reduced film TS 34%. Film elongation at break (EL) was higher in Hw films than in Lw ones, in which formate and acetate films were the highest (9% and 8%, respectively), and plasticizer increased the film EL 128%. Molecular weight of chitosan did not influence water vapor permeability (WVP) of the films. Acetate and propionate films had lower WVP than other acid types of films, and plasticizer increased film WVP about 35%. No difference was found between glycerol and sorbitol films in terms of film mechanical and water barrier properties. Lw β‐chitosan films showed significant antibacterial activity against E. coli and L. innocua. This study demonstrated that β‐chitosan films are compatible to α‐chitosan films in physicochemical properties and antibacterial activity, yet with simple sample preparation. Practical Application: β‐chitosan based edible films at molecular weight of about 300 kDa showed great antibacterial activity against Gram‐positive and Gram‐negative bacteria. The films have similar mechanical and water barrier properties to α‐chitosan based films at the similar molecular weight, but simple sample preparation procedures and more attractive color. The release of active chitosan fragment from the film matrix acts as an antibacterial agent, making β‐chitosan films suitable as intelligent food wraps or coatings for a wide range of food products to control moisture loss and prevent surface bacterial growth.     

Heat Curing of Soy Protein Films at Atmospheric and Sub-atmospheric Conditions

ABSTRACT: The effect of heat curing at atmospheric or subatmospheric conditions on selected properties (moisture content, water vapor permeability (WVP), color, tensile strength (TS), elongation (E), and total soluble matter (TSM) content) of cast soy protein isolate films was investigated. Films were heat cured at 85 °C for 6, 12, 18, or 24 h at absolute pressures of 101.3, 81.32, or 61.32 kPa. Heat-cured films had increased (P < 0.05) TS and decreased (P < 0.05) WVP and E compared to control, unheated films. Heat treatment under vacuum reduced the WVP of films faster than heat curing at atmospheric pressure. High TS values, low E values, and low TSM values were also reached within short heating time under vacuum. However, vacuum treatment increased the size and number of cavities in cured films as evidenced by scanning electron micrographs.     

Effects of storage conditions and acid solvent types on structural,mechanical and physical properties of kudzu starch (Pueraria lobata)‐chitosan composite films

Effects of acid solvents (acetic, lactic and malic acid) on properties of kudzu starch‐chitosan composite films were evaluated at −20 or 25°C during storage of 60 days. The yellowness of films enhanced, whereas water content and water vapour permeability of films declined with increasing storage time. Tensile strength of films choosing acetic and lactic acid as solvents, and solubility of all the films increased within 30 days thereafter decreased. Storage temperature had no impact on X‐ray diffraction, water content and solubility. Under the same storage conditions, the film using acetic acid as solvent presented the strongest mechanical property, the smallest solubility and the lightest colour. The film made from lactic acid solution was the most flexible and the yellowiest. The film with malic acid solvent showed the highest ordering degree, the lowest water content and the best water barrier property.     

Sorption Behavior of Crawfish Chitosan Films as Affected by Chitosan Extraction Processes and Solvent Types

Effects of chitosan extraction processes and solvent types on sorption behavior of unplasticized crawfish chitosan films were investigated. Four different chitosans prepared from crawfish shell were dissolved in 1% v/v acetic, formic, lactic, or malic acids at 1% w/v concentration. Chitosans dissolved in acetic or formic acid formed flexible and transparent films that are desirable for packaging applications. Chitosan acetate films maintained lower moisture contents at any relative humidity level compared with chitosan formate films. The type of chitosan significantly influenced the sorption isotherms of chitosan formate films but not chitosan acetate films. The Guggenheim‐Anderson‐de Boer, Oswin, and Caurie models (R²= 0.98, 0.95, and 0.95, respectively) could be used to predict sorption behavior of crawfish chitosan acetate and formate films.     

Ultraviolet Radiation Affects Physical and Molecular Properties of Soy Protein Films

Films were cast from heated, alkaline aqueous solutions of soy protein (5 g/100 mL water) and glycerin (50% w/w of protein). Control and ultraviolet (UV) irradiated (13.0, 25.9,38.9, 51.8, 77.8, or 103.7 J/m²) films were evaluated for tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and Hunter L, a, and b color values. TS increased (p<0.05) linearly while E decreased linearly with UV dosage. WVP was not affected (P>0.05) by UV irradiation. UV treatment intensified the yellowish coloration of films (increased +b values). SDS-PAGE patterns for UV-treated samples revealed bands of aggregates, increasing in intensity with UV dosage, which were absent in control samples. These changes suggested UV-induced cross-linking in films.     

Properties of triticale flour protein based films

Triticale flour proteins based films were developed. Solubility in water, water vapor permeability (WVP), and mechanical properties of triticale films are presented. The effects of thermal treatments and glycerol concentration were also evaluated. WVP values were in the range 0.10-4.22 × 10⁻¹⁰ g m⁻¹ s⁻¹ Pa⁻¹. Tensile strength (TS) and percentage of elongation (%E) were in the range 2.9-0.20 MPa and 250-110% respectively. Total soluble matter (TSM), WVP, and %E decreased with the increase in the curing temperature. More plasticized films presented greater TSM, WVP, %E and lower values of TS. At a giving temperature (T) and glycerol concentration, an increase in relative humidity (RH) resulted in higher values of TSM, WVP, %E and lower TS values. It was observed that in films with the same treatments and conditioning, WVP increased with the increase in measurement temperature. Triticale proteins showed suitable film-forming capacity for the formulation of biodegradable films.     

甘油与甲基纤维素对高直链玉米淀粉- 壳聚糖复合膜性能的影响

以高直链玉米淀粉(HACS)和壳聚糖(CS)为基本材料,甘油为增塑剂,甲基纤维素(MC)为增强剂制备可食性复合膜,研究高直链玉米淀粉与壳聚糖的质量比,甘油的添加量以及甲基纤维素的添加量对复合膜物理性能的影响,包括抗拉强度(TS)、断裂伸长率(E)、水蒸气透过系数(WVP)和色度。结果表明,壳聚糖添加量的增大与甘油添加量的增加都使高直链玉米淀粉- 壳聚糖复合膜的抗拉强度降低,断裂伸长率和WVP 显著增大,膜颜色变黄;甲基纤维素的添加改善了复合膜的机械性能和WVP,随着甲基纤维素添加量的增加,复合膜的抗拉强度和断裂伸长率都随之增大,WVP 逐渐降低,且对膜的颜色没有显著影响。     

响应面法优化纳米SiOx/鸡蛋清蛋白可食性膜的琥珀酰化改性工艺

目的：以鸡蛋清蛋白为原料,制备纳米SiOx/鸡蛋清蛋白可食性膜,研究琥珀酰化改性工艺对膜性能的影响。方法：以琥珀酸酐添加量、反应时间、反应温度及反应pH值为影响因素,以拉伸强度、断裂伸长率、水蒸气透过系数及透油系数为响应值,采用单因素试验和响应面分析法,优化可食性膜的琥珀酰化改性工艺。结果：建立了回归模型,优化琥珀酰化改性工艺为琥珀酸酐添加量0.70 g、反应时间40.35 min、反应温度34.87 ℃、反应pH 8.30,在此条件下可食性膜拉伸强度、断裂伸长率、水蒸气透过系数及透油系数的预测值分别为4.935 MPa、75.446%、3.499 g·mm/（m2·d·kPa）、0.874 g·mm/（m2·d）,验证值为：（4.891±0.126）MPa、（73.560±4.329）%、（3.651±0.097）g·mm/（m2·d·kPa）、（0.914±0.008）g·mm/（m2·d）,与之接近,优化结果可靠。结论：琥珀酸酐添加量和反应pH值是影响膜性能的主要因素。     

Effect of pH and addition of corn oil on the properties of whey protein isolate-based films using response surface methodology

Response surface methodology (RSM) was used to investigate pH and corn oil (CO) effects on the properties of films formed from whey protein isolate (WPI). Test films were evaluated for tensile strength (TS), puncture strength (PT), percentage elongation at break point (E), water vapour permeability (WVP) and oxygen permeability (OP). TS of WPI films increased with increasing pH, while addition of CO produced no trend. However, when WPI solution pH increased >10.0, film TS generally decreased with CO addition (>11%). E values increased dramatically with increasing levels of CO when pH for WPI solutions were >8.5. However, pH had no effect on E values. WPI solutions possessing high pH values (maximum pH value of 10.62) produced WPI films with the highest PT values. WVP had a quadratic relationship with pH and CO addition. OP had an inversely linear relationship with increasing pH (6.5–10.5) and a quadratic relationship with CO addition. Optimal pH (9.88) and CO level (2.93%), determined from physical test film data, were predicted by RSM.     

Chitosan coating minimises eggshell breakage and improves egg quality

The interior quality of eggs, shell impact strength, and consumer perception of eggs coated with chitosan containing an organic acid (acetic, lactic and propionic) were evaluated. Uncoated eggs had the highest albumen pH and lowest albumen viscosity. The viscosity of eggs coated with chitosan and lactic or propionic acids were the highest. Chitosan coating also improved shell strength with chitosan + lactic acid being the best coating in this regard. The colour of shell and yolk as measured by lightness (L*), a*, b*, chroma and hue of coated and uncoated eggs were not significantly different but the difference was detected in the colour of albumen, which is an effective indication of freshness and egg quality. Based on sensory evaluation, consumers could not differentiate coated eggs from uncoated eggs; thus the general acceptability of the coated eggs was the same as uncoated eggs. This study shows a great potential of using chitosan and lactic acid mixture as a coating material for egg coating to extend the shelf life. It has no effect on consumer acceptability of the product. Copyright © 2007 Society of Chemical Industry     

Fatty Acid Concentration Effect on Tensile Strength, Elongation, and Water Vapor Permeability of Laminated Edible Films

Water vapor permeability (WVP), tensile strength (TS), and elongation (E) were investigated in laminated methyl cellulose/corn zein-fatty acid films. They were prepared by casting corn zein-fatty acid solutions onto methyl cellulose films. WVP decreased as chain length and concentration of fatty acids increased. The TS of laminated edible film containing palmitic acid decreased as palmitic acid increased. The TS of films containing stearic-palmitic acid blends showed similar trends but there were no significant differences among blends. The TS of the film containing lauric acid was maximum at 30% lauric acid concentration. The E values for films containing fatty acids varied inversely with TS.     

Effectiveness of chitosan‐based coating in improving shelf‐life of eggs

Despite eggs having a natural packaging—shell—they are perishable and can lose their quality during storage. Chitosan‐based coatings were applied to shell eggs to examine potential effects on egg quality properties (weight loss, Haugh unit, yolk index) during 4 weeks of storage. Mineral amounts in yolks were also evaluated after 4 weeks of storage. Three chitosan‐based coatings produced with organic acids (acetic‐(C‐AA), lactic‐(C‐LA), and propionic (C‐PA)) were evaluated on shelf‐life enhancements of fresh egg quality. All chitosan‐coated eggs showed greater interior quality than the non‐coated eggs. The coatings significantly maintained weight loss compared to the control specimen (4.96%). Lower weight loss (3.45% for C‐PA, 3.53% for C‐LA) was observed in the coated eggs. Eggshell chitosan coat containing lactic and propionic acids maintained higher Haugh unit and yolk index than eggs coated with acetic acid. Uncoated (UC) eggs changed from grade ‘A’ to ‘B’ after 1 week of storage. Chitosan‐based coating containing lactic and propionic acids maintained eggs in grade ‘A’ for 4 weeks. Haugh unit showed that C‐LA and C‐PA effectively maintained eggs at grade ‘A’ quality for at least 3 weeks more than control and 1 week more than C‐AA. Results also indicated that the chitosan coating maintained mineral amounts at nutritional values (especially calcium, iron and magnesium concentration) in yolks after 4 weeks storage. Copyright © 2006 Society of Chemical Industry     

壳聚糖成膜溶液及其膜相关性质研究

以不同体积分数的乙酸溶液为分散剂,不同质量浓度的山梨醇为增塑剂,配制不同质量浓度的两种脱乙酰度壳聚糖溶液,探讨不同质量浓度基质对壳聚糖溶液pH值和电导率的影响,阐述壳聚糖溶液在成膜过程中各离子的聚合情况。对壳聚糖成膜溶液的流变学性质进行研究,并对其形成的膜进行表征,分析山梨醇对壳聚糖成膜溶液及其膜性质的影响。结果表明：壳聚糖成膜溶液体系中,主要是山梨醇、乙酸与壳聚糖中的各种离子结合形成黏稠的溶液。含与不含山梨醇作为增塑剂的壳聚糖成膜溶液均表现出假塑性流体,山梨醇与两种脱乙酰度的壳聚糖均有很好的相容性,能够形成均匀、连续的膜,使壳聚糖膜的吸热峰和放热峰发生一定的迁移,对其热稳定性有一定的影响。     

The antimicrobial,mechanical, physical and structural properties of chitosan–gallic acid films

Chitosan films incorporated with various concentrations of gallic acid were prepared and investigated for antimicrobial, mechanical, physical and structural properties. Four bacterial strains that commonly contaminate food products were chosen as target bacteria to evaluate the antimicrobial activity of the prepared gallic acid–chitosan films. The incorporation of gallic acid significantly increased the antimicrobial activities of the films against Escherichia coli, Salmonella typhimurium, Listeria innocua and Bacillus subtilis. Chitosan films incorporated with 1.5 g/100 g gallic acid showed the strongest antimicrobial activity. It was also found that tensile strength (TS) of chitosan film was significantly increased when incorporating 0.5 g/100 g gallic acid. Inclusion of 0.5 g/100 g gallic acid also significantly decreased water vapor permeability (WVP) and oxygen permeability (OP). Microstructure of the films was investigated by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) and it was found that gallic acid was dispersed homogenously into the chitosan matrix.     

Mechanical and Barrier Properties of Egg Albumen Films

Films were cast and dried from heated, alkaline aqueous egg albumen solutions containing glycerin (GLY) at 30, 40, or 50% w/w of protein, polyethylene glycol (PEG) at 50 or 60%, or sorbitol (S) at 50 or 60% as plasticizers. PEG-plasticized (60%) films also were prepared by substituting 10, 30, 50, or 70% of albumen with yolk solids. Film tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and Hunter color values were measured. At a plasticizer content of 50%, films with S had the lowest WVP while films with PEG had the greatest E. S- and PEG-plasticized films had greater TS than GLY-plasticized films. Yolk solids decreased film TS, E, and WVP while increasing film yellowness.     

Heat Curing of Soy Protein Films at Selected Temperatures and Pressures

Vacuum and temperature effects on moisture content, water vapor permeability (WVP), color (L, a, b, and ΔE), tensile strength (TS), elongation (E), and total soluble matter (TSM) of soy protein isolate (SPI) films were examined. SPI films were cured at 60, 72.5, or 85 °C and at 101.3, 81.32, or 61.32 kPa for 24 h. As a result of heat-curing moisture content, WVP, E, and TSM decreased, and total color difference and TS increased. Pressure, individually and interactively with temperature, significantly affected film moisture content, TS, and TSM.     

Antibacterial activity of chitosans and chitosan oligomers with different molecular weights

Antibacterial activities of six chitosans and six chitosan oligomers with different molecular weights (Mws) were examined against four gram-negative (Escherichia coli, Pseudomonas fluorescens, Salmonella typhimurium, and Vibrio parahaemolyticus) and seven gram-positive bacteria (Listeria monocytogenes, Bacillus megaterium, B. cereus, Staphylococcus aureus, Lactobacillus plantarum, L. brevis, and L. bulgaricus). Chitosans showed higher antibacterial activities than chitosan oligomers and markedly inhibited growth of most bacteria tested although inhibitory effects differed with Mws of chitosan and the particular bacterium. Chitosan generally showed stronger bactericidal effects with gram-positive bacteria than gram-negative bacteria in the presence of 0.1% chitosan. The minimum inhibitory concentration (MIC) of chitosans ranged from 0.05% to >0.1% depending on the bacteria and Mws of chitosan. As a chitosan solvent, 1% acetic acid was effective in inhibiting the growth of most of the bacteria tested except for lactic acid bacteria that were more effectively suppressed with 1% lactic or formic acids. Antibacterial activity of chitosan was inversely affected by pH (pH 4.5-5.9 range tested), with higher activity at lower pH value.     

十二烷基磺酸钠(SDS)在大豆分离蛋白基可食性膜中应用

该文报道研究十二烷基磺酸钠应用于以甘油作为增塑剂的大豆蛋白基可食性膜后对其物理性质影响。研究结果表明:当SDS添加量为40%(十二烷基磺酸钠质量/大豆分离蛋白质量)时,薄膜抗拉强度(TS)值显著(p<0.05)减少43%,最大断裂伸长率(E)值显著(p<0.05)增加至少5%,水分含量(MC)值显著减少(p<0.05),总可溶性物质含量(TSM)值显著增加(p<0.05);当SDS添加量>10%时,WVP值下降50%;SDS添加量为20%、30%、40%时,膜颜色值为显著+b (p<0.05),即黄色值增加。